1. Technical Field
The present invention relates to an antenna apparatus. In particular, the present invention relates to an antenna apparatus for directly and wirelessly transmitting and receiving a wireless digital signal.
2. Background Art
Wideband antenna apparatuses for directly and wirelessly transmitting and receiving wireless digital signals have been widespread. Patent Document 1 discloses a microstrip antenna according to a prior art, in which the occurrence of a higher harmonic mode is reduced within a wide band. Paying attention to the distribution of the respective resonance modes of the microstrip antenna, the Patent Document 1 controls the antenna characteristics by suppressing higher-order frequency resonance modes by providing notched portions at four corners of a radiation conductor plate formed on a surface of a dielectric substrate.    Patent Document 1: Japanese patent laid-open publication No. JP 05-129825-A.    Patent Document 2: Japanese patent laid-open publication No. JP 2005-278067-A.    Patent Document 3: Japanese patent laid-open publication No. JP 2005-079972-A.    Non-Patent Document 1: Ramesh Garg, et al., “Microstrip antenna Design Handbook”, Artech House, pp. 8-12, November 2000.    Non-Patent Document 2: Osamu Koyasu at al., “Improvement of Transmission Characteristic with Passive Equalizer and Fast Ethernet Cable” The Institute of Electronics, Information and Communication Engineers, Transaction C, Vol. J87-C, No. 11, pp. 873-880, Nov. 1, 2004.